The four big questions for Bert van Marwijk's Socceroos XI

Four positions remain up for grabs in the Socceroos' side for their World Cup opener with France.

Two days out from their date with Les Bleus in Kazan, Australia boast a fit and healthy squad, with all 23 players training once more at the Stadium Trudovye Rezervy on Wednesday.

Seven players appear guaranteed their positions in Bert van Marwijk's side to play the world No.7s, based on the Dutchman's preferences and comments.

Mat Ryan, long Australia's No.1 goalkeeper, is a lock to start.

While the lead-up performances of the Socceroos' back four have left a little to be desired, van Marwijk's reticence to even bring in substitutes through their warm-up friendlies suggests he is firm in his mind about his defence.

Aziz Behich and Josh Risdon will start as the full-backs, as converted midfielder Mark Milligan partners Trent Sainsbury in the centre.

Is the skipper a lock to start? Pic: Getty

Aaron Mooy, arguably Australia's most important player, will play as one of the holding midfielders.

But the only man assured of a role in the Socceroos' front four is right winger Mat Leckie.

The left-sided attacker, striker and attacking midfielder positions are giving van Marwijk headaches, along with the decision on who will partner Mooy at the base of midfield.

Andrew Nabbout, one of the contenders to start up front, said he was "100 per cent ready" for the marquee occasion should van Marwijk call his name.

"He wants that pressing at the front," Nabbout said.

"He wants people to put teams under pressure and run in from behind. That's my game

"Hopefully I get that chance and I'm going to keep on doing that."

Jackson Irvine, who is in the frame to start as a No.10 but behind incumbent Tom Rogic, said he was relaxed about the call.

"I'm glad I've been spoken of, and maybe given him a selection headache," he said.

"There's so many talented players in our squad, and maybe a few positions up for grabs on the next few days, but the manager is very pragmatic and he'll prepare the team well."

SOCCEROOS SELECTION HEAD-SCRATCHERS:

CENTRAL MIDFIELD: Mile Jedinak v Massimo Luongo

It speaks volumes for Luongo's development that he could keep Australia's captain fantastic out of the starting line-up. With Jedinak arriving late into camp, the QPR man was preferred in lead-in friendlies, but Jedinak impressed in the second half against Hungary.

ATTACKING MIDFIELD: Tom Rogic v Jackson Irvine

Rogic is Australia's most talented attacker and finally gets the chance to shine on a World Cup stage after injury cruelled his chances in Brazil. But Irvine offers more dynamic play and never gives up. Might not start against France but should in one of the group matches.

LEFT ATTACKER: Robbie Kruse v Daniel Arzani

Arzani's match-winning cameo against Hungary has given his boss food for thought. Though he is also at his first World Cup, Kruse's experience should give him the edge. But might the Dutchman throw in the tournament's youngest player from the get-go?

STRIKER: Andrew Nabbout v Tomi Juric

If the World Cup year was 2017, this is a completely different answer; Ange Postecoglou would be starting Juric every day of the week. Van Marwijk's more muscular style suggests the Nabbout, the bolt from the blue, will be his choice, as he has been in this year's friendlies.